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Rework backend loading.
This is preliminary work towards fixing the runtime detection of default backend problem (the first step being to make it easier to check whether a backend *can* be loaded). No publically visible API is changed. Backend loading now defines default versions of `backend_version`, `draw_if_interactive`, and `show` using the same inheritance strategy as builtin backends do. For non-interactive backends (i.e., `FigureManager == FigureManagerBase`), restore the default implementation of `show()` that prints a warning when run from a console (the backend refactor accidentally removed this error message as it provided a silent default `show()`). The `_Backend` class had to be moved to the end of the module as `FigureManagerBase` needs to be defined first. The `ShowBase` class had to be moved even after that as it depends on the `_Backend` class.
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-166
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‎lib/matplotlib/backend_bases.py

+128-114
Original file line numberDiff line numberDiff line change
@@ -41,13 +41,15 @@
4141
from contextlib import contextmanager
4242
from functools import partial
4343
import importlib
44+
import inspect
4445
import io
4546
import os
4647
import sys
4748
import time
4849
import warnings
4950

5051
import numpy as np
52+
import matplotlib
5153
import matplotlib.cbook as cbook
5254
import matplotlib.colors as colors
5355
import matplotlib.transforms as transforms
@@ -135,120 +137,6 @@ def get_registered_canvas_class(format):
135137
return backend_class
136138

137139

138-
class _Backend(object):
139-
# A backend can be defined by using the following pattern:
140-
#
141-
# @_Backend.export
142-
# class FooBackend(_Backend):
143-
# # override the attributes and methods documented below.
144-
145-
# The following attributes and methods must be overridden by subclasses.
146-
147-
# The `FigureCanvas` and `FigureManager` classes must be defined.
148-
FigureCanvas = None
149-
FigureManager = None
150-
151-
# The following methods must be left as None for non-interactive backends.
152-
# For interactive backends, `trigger_manager_draw` should be a function
153-
# taking a manager as argument and triggering a canvas draw, and `mainloop`
154-
# should be a function taking no argument and starting the backend main
155-
# loop.
156-
trigger_manager_draw = None
157-
mainloop = None
158-
159-
# The following methods will be automatically defined and exported, but
160-
# can be overridden.
161-
162-
@classmethod
163-
def new_figure_manager(cls, num, *args, **kwargs):
164-
"""Create a new figure manager instance.
165-
"""
166-
# This import needs to happen here due to circular imports.
167-
from matplotlib.figure import Figure
168-
fig_cls = kwargs.pop('FigureClass', Figure)
169-
fig = fig_cls(*args, **kwargs)
170-
return cls.new_figure_manager_given_figure(num, fig)
171-
172-
@classmethod
173-
def new_figure_manager_given_figure(cls, num, figure):
174-
"""Create a new figure manager instance for the given figure.
175-
"""
176-
canvas = cls.FigureCanvas(figure)
177-
manager = cls.FigureManager(canvas, num)
178-
return manager
179-
180-
@classmethod
181-
def draw_if_interactive(cls):
182-
if cls.trigger_manager_draw is not None and is_interactive():
183-
manager = Gcf.get_active()
184-
if manager:
185-
cls.trigger_manager_draw(manager)
186-
187-
@classmethod
188-
def show(cls, block=None):
189-
"""Show all figures.
190-
191-
`show` blocks by calling `mainloop` if *block* is ``True``, or if it
192-
is ``None`` and we are neither in IPython's ``%pylab`` mode, nor in
193-
`interactive` mode.
194-
"""
195-
if cls.mainloop is None:
196-
return
197-
managers = Gcf.get_all_fig_managers()
198-
if not managers:
199-
return
200-
for manager in managers:
201-
manager.show()
202-
if block is None:
203-
# Hack: Are we in IPython's pylab mode?
204-
from matplotlib import pyplot
205-
try:
206-
# IPython versions >= 0.10 tack the _needmain attribute onto
207-
# pyplot.show, and always set it to False, when in %pylab mode.
208-
ipython_pylab = not pyplot.show._needmain
209-
except AttributeError:
210-
ipython_pylab = False
211-
block = not ipython_pylab and not is_interactive()
212-
# TODO: The above is a hack to get the WebAgg backend working with
213-
# ipython's `%pylab` mode until proper integration is implemented.
214-
if get_backend() == "WebAgg":
215-
block = True
216-
if block:
217-
cls.mainloop()
218-
219-
# This method is the one actually exporting the required methods.
220-
221-
@staticmethod
222-
def export(cls):
223-
for name in ["FigureCanvas",
224-
"FigureManager",
225-
"new_figure_manager",
226-
"new_figure_manager_given_figure",
227-
"draw_if_interactive",
228-
"show"]:
229-
setattr(sys.modules[cls.__module__], name, getattr(cls, name))
230-
231-
# For back-compatibility, generate a shim `Show` class.
232-
233-
class Show(ShowBase):
234-
def mainloop(self):
235-
return cls.mainloop()
236-
237-
setattr(sys.modules[cls.__module__], "Show", Show)
238-
return cls
239-
240-
241-
class ShowBase(_Backend):
242-
"""
243-
Simple base class to generate a show() callable in backends.
244-
245-
Subclass must override mainloop() method.
246-
"""
247-
248-
def __call__(self, block=None):
249-
return self.show(block=block)
250-
251-
252140
class RendererBase(object):
253141
"""An abstract base class to handle drawing/rendering operations.
254142
@@ -3367,3 +3255,129 @@ def set_message(self, s):
33673255
Message text
33683256
"""
33693257
pass
3258+
3259+
3260+
class _Backend(object):
3261+
# A backend can be defined by using the following pattern:
3262+
#
3263+
# @_Backend.export
3264+
# class FooBackend(_Backend):
3265+
# # override the attributes and methods documented below.
3266+
3267+
# May be overridden by the subclass.
3268+
backend_version = "unknown"
3269+
# The `FigureCanvas` class must be overridden.
3270+
FigureCanvas = None
3271+
# For interactive backends, the `FigureManager` class must be overridden.
3272+
FigureManager = FigureManagerBase
3273+
# The following methods must be left as None for non-interactive backends.
3274+
# For interactive backends, `trigger_manager_draw` should be a function
3275+
# taking a manager as argument and triggering a canvas draw, and `mainloop`
3276+
# should be a function taking no argument and starting the backend main
3277+
# loop.
3278+
trigger_manager_draw = None
3279+
mainloop = None
3280+
3281+
# The following methods will be automatically defined and exported, but
3282+
# can be overridden.
3283+
3284+
@classmethod
3285+
def new_figure_manager(cls, num, *args, **kwargs):
3286+
"""Create a new figure manager instance.
3287+
"""
3288+
# This import needs to happen here due to circular imports.
3289+
from matplotlib.figure import Figure
3290+
fig_cls = kwargs.pop('FigureClass', Figure)
3291+
fig = fig_cls(*args, **kwargs)
3292+
return cls.new_figure_manager_given_figure(num, fig)
3293+
3294+
@classmethod
3295+
def new_figure_manager_given_figure(cls, num, figure):
3296+
"""Create a new figure manager instance for the given figure.
3297+
"""
3298+
canvas = cls.FigureCanvas(figure)
3299+
manager = cls.FigureManager(canvas, num)
3300+
return manager
3301+
3302+
@classmethod
3303+
def draw_if_interactive(cls):
3304+
if cls.trigger_manager_draw is not None and is_interactive():
3305+
manager = Gcf.get_active()
3306+
if manager:
3307+
cls.trigger_manager_draw(manager)
3308+
3309+
@classmethod
3310+
def show(cls, block=None):
3311+
"""Show all figures.
3312+
3313+
`show` blocks by calling `mainloop` if *block* is ``True``, or if it
3314+
is ``None`` and we are neither in IPython's ``%pylab`` mode, nor in
3315+
`interactive` mode.
3316+
"""
3317+
if cls.mainloop is None:
3318+
frame = inspect.currentframe()
3319+
while frame:
3320+
if frame.f_code.co_filename in [
3321+
"<stdin>", "<ipython console>"]:
3322+
warnings.warn("""\
3323+
Your currently selected backend does not support show().
3324+
Please select a GUI backend in your matplotlibrc file ('{}')
3325+
or with matplotlib.use()""".format(matplotlib.matplotlib_fname()))
3326+
break
3327+
else:
3328+
frame = frame.f_back
3329+
return
3330+
managers = Gcf.get_all_fig_managers()
3331+
if not managers:
3332+
return
3333+
for manager in managers:
3334+
manager.show()
3335+
if block is None:
3336+
# Hack: Are we in IPython's pylab mode?
3337+
from matplotlib import pyplot
3338+
try:
3339+
# IPython versions >= 0.10 tack the _needmain attribute onto
3340+
# pyplot.show, and always set it to False, when in %pylab mode.
3341+
ipython_pylab = not pyplot.show._needmain
3342+
except AttributeError:
3343+
ipython_pylab = False
3344+
block = not ipython_pylab and not is_interactive()
3345+
# TODO: The above is a hack to get the WebAgg backend working with
3346+
# ipython's `%pylab` mode until proper integration is implemented.
3347+
if get_backend() == "WebAgg":
3348+
block = True
3349+
if block:
3350+
cls.mainloop()
3351+
3352+
# This method is the one actually exporting the required methods.
3353+
3354+
@staticmethod
3355+
def export(cls):
3356+
for name in ["backend_version",
3357+
"FigureCanvas",
3358+
"FigureManager",
3359+
"new_figure_manager",
3360+
"new_figure_manager_given_figure",
3361+
"draw_if_interactive",
3362+
"show"]:
3363+
setattr(sys.modules[cls.__module__], name, getattr(cls, name))
3364+
3365+
# For back-compatibility, generate a shim `Show` class.
3366+
3367+
class Show(ShowBase):
3368+
def mainloop(self):
3369+
return cls.mainloop()
3370+
3371+
setattr(sys.modules[cls.__module__], "Show", Show)
3372+
return cls
3373+
3374+
3375+
class ShowBase(_Backend):
3376+
"""
3377+
Simple base class to generate a show() callable in backends.
3378+
3379+
Subclass must override mainloop() method.
3380+
"""
3381+
3382+
def __call__(self, block=None):
3383+
return self.show(block=block)

‎lib/matplotlib/backends/__init__.py

+24-43
Original file line numberDiff line numberDiff line change
@@ -3,10 +3,11 @@
33

44
import six
55

6-
import matplotlib
7-
import inspect
6+
import importlib
87
import traceback
9-
import warnings
8+
9+
import matplotlib
10+
from matplotlib.backend_bases import _Backend
1011

1112

1213
backend = matplotlib.get_backend()
@@ -45,51 +46,31 @@ def pylab_setup(name=None):
4546
'''
4647
# Import the requested backend into a generic module object
4748
if name is None:
48-
# validates, to match all_backends
4949
name = matplotlib.get_backend()
50-
if name.startswith('module://'):
51-
backend_name = name[9:]
52-
else:
53-
backend_name = 'backend_' + name
54-
backend_name = backend_name.lower() # until we banish mixed case
55-
backend_name = 'matplotlib.backends.%s' % backend_name.lower()
56-
57-
# the last argument is specifies whether to use absolute or relative
58-
# imports. 0 means only perform absolute imports.
59-
backend_mod = __import__(backend_name, globals(), locals(),
60-
[backend_name], 0)
61-
62-
# Things we pull in from all backends
63-
new_figure_manager = backend_mod.new_figure_manager
64-
65-
# image backends like pdf, agg or svg do not need to do anything
66-
# for "show" or "draw_if_interactive", so if they are not defined
67-
# by the backend, just do nothing
68-
def do_nothing_show(*args, **kwargs):
69-
frame = inspect.currentframe()
70-
fname = frame.f_back.f_code.co_filename
71-
if fname in ('<stdin>', '<ipython console>'):
72-
warnings.warn("""
73-
Your currently selected backend, '%s' does not support show().
74-
Please select a GUI backend in your matplotlibrc file ('%s')
75-
or with matplotlib.use()""" %
76-
(name, matplotlib.matplotlib_fname()))
77-
78-
def do_nothing(*args, **kwargs):
79-
pass
80-
81-
backend_version = getattr(backend_mod, 'backend_version', 'unknown')
82-
83-
show = getattr(backend_mod, 'show', do_nothing_show)
84-
85-
draw_if_interactive = getattr(backend_mod, 'draw_if_interactive',
86-
do_nothing)
50+
backend_name = (name[9:] if name.startswith("module://")
51+
else "matplotlib.backends.backend_{}".format(name.lower()))
8752

53+
backend_mod = importlib.import_module(backend_name)
54+
Backend = type(str("Backend"), (_Backend,), vars(backend_mod))
8855
matplotlib.verbose.report('backend %s version %s' %
89-
(name, backend_version))
56+
(name, Backend.backend_version))
9057

9158
# need to keep a global reference to the backend for compatibility
9259
# reasons. See https://github.com/matplotlib/matplotlib/issues/6092
9360
global backend
9461
backend = name
95-
return backend_mod, new_figure_manager, draw_if_interactive, show
62+
63+
# We want to get functions out of a class namespace and call them *without
64+
# the first argument being an instance of the class*. This works directly
65+
# on Py3. On Py2, we need to remove the check that the first argument be
66+
# an instance of the class. The only relevant case is if `.im_self` is
67+
# None, in which case we need to use `.im_func` (if we have a bound method
68+
# (e.g. a classmethod), everything is fine).
69+
def _dont_check_first_arg(func):
70+
return (func.im_func if getattr(func, "im_self", 0) is None
71+
else func)
72+
73+
return (backend_mod,
74+
_dont_check_first_arg(Backend.new_figure_manager),
75+
_dont_check_first_arg(Backend.draw_if_interactive),
76+
_dont_check_first_arg(Backend.show))

‎lib/matplotlib/backends/backend_pdf.py

+1-3
Original file line numberDiff line numberDiff line change
@@ -2599,11 +2599,9 @@ def print_pdf(self, filename, **kwargs):
25992599
file.close()
26002600

26012601

2602-
class FigureManagerPdf(FigureManagerBase):
2603-
pass
2602+
FigureManagerPdf = FigureManagerBase
26042603

26052604

26062605
@_Backend.export
26072606
class _BackendPdf(_Backend):
26082607
FigureCanvas = FigureCanvasPdf
2609-
FigureManager = FigureManagerPdf

‎lib/matplotlib/backends/backend_ps.py

+1-3
Original file line numberDiff line numberDiff line change
@@ -1728,8 +1728,7 @@ def pstoeps(tmpfile, bbox=None, rotated=False):
17281728
shutil.move(epsfile, tmpfile)
17291729

17301730

1731-
class FigureManagerPS(FigureManagerBase):
1732-
pass
1731+
FigureManagerPS = FigureManagerBase
17331732

17341733

17351734
# The following Python dictionary psDefs contains the entries for the
@@ -1775,4 +1774,3 @@ class FigureManagerPS(FigureManagerBase):
17751774
@_Backend.export
17761775
class _BackendPS(_Backend):
17771776
FigureCanvas = FigureCanvasPS
1778-
FigureManager = FigureManagerPS

‎lib/matplotlib/backends/backend_svg.py

+2-3
Original file line numberDiff line numberDiff line change
@@ -1251,8 +1251,8 @@ def _print_svg(self, filename, svgwriter, **kwargs):
12511251
def get_default_filetype(self):
12521252
return 'svg'
12531253

1254-
class FigureManagerSVG(FigureManagerBase):
1255-
pass
1254+
1255+
FigureManagerSVG = FigureManagerBase
12561256

12571257

12581258
svgProlog = """\
@@ -1266,4 +1266,3 @@ class FigureManagerSVG(FigureManagerBase):
12661266
@_Backend.export
12671267
class _BackendSVG(_Backend):
12681268
FigureCanvas = FigureCanvasSVG
1269-
FigureManager = FigureManagerSVG

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